This invention relates to improved cosmetically acceptable compositions for topical application to skin, particularly for the prevention or treatment of acne.
Acne is a follicular dermatosis. The comedo, which is the initial lesion of acne, resulting from the impaction of horny cells within the sebaceous follicle, develops in several stages. Primary comedones develop first as microcomedones where the follicular ostium begins to be distended by horny; material to form keratin plugs. The first visible lesion is the closed comedo or whitehead. Dilatation of the follicular ostium by dark pigmented horny material marks the onset of an open comedo or blackhead. Subsequent rupture of closed or open comedones results in formation of secondary comedones which are generally larger and more irregularly shaped.
The bricks of the horny framework of comedones are corneocytes (i.e., individual dead skin cells) which are held together by a cement-like substance of extracellular lipids. Closed and open comedones develop into the nodules and pustules identified with inflammatory acne. Although there are multiple factors that appear to be operative in the pathogenesis of acne, it is the formation of keratin plugs (i.e.,
It is therefore apparent that a treatment directed at preventing or dissolving such keratin plugs (keratolysis) would reduce the compaction necessary to produce the comedo as well as helping to unseat existing comedones (comedolysis).
Salicylic acid is a well recognized anti-acne active ingredient which causes a reduction in intercellular cohesion of the corneocytes (see C. Huber et al, Arch. Derm. Res. 257, 293-297, 1977), thereby dissolving the existing keratin plugs as well as preventing the formation of new ones. In order to best exert its keratolytic and comedolytic effect, the ideal anti-acne composition should deliver and retain optimal concentrations of salicylic acid in the stratum corneum with less penetration through the skin and into the general circulation.
According to the present invention, an effective antiacne composition is provided whereby substantial amounts of salcylic acid can be deposited into the stratum corneum with minimal penetration through the skin. The resultant increased efficacy of salicylic acid, as demonstrated by increased desquamation of corneocytes, occurs with less potential for irritation, drying of skin and systemic side effects.